DESCRIPTION (Applicant's abstract): The main olfactory and vomeronasal systems are major chemosensory systems that guide animal behavior in response to changing environmental cues. The dual olfactory system hypothesis postulates that these two systems comprise parallel pathways through the telencephalon and, by virtue of these connections, are involved in different aspects of behavioral response to chemical stimuli. Recent findings indicate that neurons in the main olfactory and vomeronasal systems terminate in different nuclei of the amygdaloid complex and converge on other telencephalic nuclei. These anatomical relationships and the roles of the central neural structures involved in response to prey-derived chemicals are the subjects of our research. We are using snakes to study the vomeronasal and olfactory systems and the interactions between these two systems because snakes have extraordinary well-developed vomeronasal systems that are of critical importance in naturally occurring behaviors such as courtship, prey discrimination and aggregation. Parallel work in other laboratories using mammals has demonstrated the applicability and generality of our findings to other vertebrates. We will continue to explore the anatomical connections of these systems and to study the roles of their central nervous system components in responding to prey chemicals by determining the effects of various lesions on discriminated response to prey chemicals. The sites of their lesions will be the terminations of mitral cell axons from the olfactory bulbs and their further projections in the central nervous system.